Obtaining useful products from liquors resulting from manufacturing cellulose by sulfite processes.



NITED STATES I CARL DANIEL EKMAN, OF LONDON, ENGLAND.

OBTAINING USEFUL PRODUCTS FROM LIQUORS RESULTING FROM MANUFACTURING CELLULOSE BY SULFITE PROCESSES.

SPECIFICATION forming part of Letters Patent Noa 640,186, dated January 2, 1900.

Application filed July 21, 1899. Serial No. 724,607. No specimens.)

To all whom it may concern.-

Be it known that I, CAR DANIEL EKMAN, of London, England, have invented certain new and useful Improvements in Obtaining Useful Products from the Liquors Resulting from the Manufacture of Cellulose or Fibers by the Sulfite Process, of which the following is a specification.

The object of this invention is to obtain useful products-such, for example, as sizing or stiffening materials-from the liquors, generally called sulfite liquor, resulting from the manufacture of cellulose or fibers from wood or other fibrous plants by boiling under pressure with a sulfite solution or a solution containing sulfurous acid and a base such as potash, soda, magnesia, or lime.

According to this invention the sulfite liquor is treated with oxid of zinc either at the ordinary temperature or at an elevated temperature. The oxid of zinc may either be introduced into the sulfite liquor in the form of oxid or I may use instead thereof a zinc salt which is soluble in the sulfite liquor-such, for example, as sulfate of zinctogether with a suitable base-such, for example, as sodaash-by which the oxid of zinc will be precipitated. Chemically-prepared carbonate of zinc can also be used; but it acts slower than oxid and offers no special advantages. The oxid of zinc appears to form a chemical combination with some substances in the sulfite liquor, and after evaporation a thick concentrated liquor is obtained which can be utilized for sizing or stiffening purposes or in the manner described in my Patent No. 550,712, dated December 3, 1895, for the manufacture of a product resembling or having properties similar to those of dextrine. This product when made with liquor treated according to the present invention is of better quality and color than that obtained from liquor treated as described in my said former patent.

One way in which the present invention can be carried into effect is to place the sulfite liquor in an agitator-tank lined with lead or made of an acid-resisting material and to heat the liquor by a lead coil or other suitable arrangement to about 80 to 90 centigrade and to then add an excess of oxid of zinc in powder under agitation, the heating being con tinued for four to five hours until the liquor has been saturated with the oxid of zinc and shows a strong alkaline reaction on litmus-paper. The liquor is separated from the precipitate by settling or filtering or by first partly settling and then clearing by filtration. This clear liquor is now evaporated, care being taken that its color does not suffer by using a too-high temperature or from other causes. I therefore prefer to evaporate the prepared liquor in a vacuum.

A smaller amount of oxid of zinc than is necessary to saturate the liquor may be used for some purposes, as even a very small amount generally improves the color of the products obtained from the liquor; but this as well as the time and degree of heating chiefly depend on the special purposes for which the liquor is intended.

If for the sake of economy not enough oxid of zinc has been used to saturate the liquor, but for the sake of evaporation or for any other cause it is desired to have an alkaline liquor, the necessary quantity of a suitable base, as magnesia or soda, is added.

Another way of treating the sulfite liquor is to pass it through a layer of oxid of zinc once or oftener until the liquor gets saturated. Ihe clear saturated liquor is then evaporated, as usual, and can be used for the manufacture of the dextrine-like product described in my former patent or for other purposes. Further, for the sake of economy the oxid of zinc may be partly replaced by a cheaper oxid, and this can be done by adding soda-ash to the sulfite liquor before it passes through the oxid of zinc. A convenient way to do this is to heat the liquor by a lead steamcoil in an agitator-tank, as above described, to about 40 to centigrade under agitation until the liquor shows a nearly neutral reac tion on Very sensitive blue litmus-paper and then to pass this so-prepared liquor through oxid of zinc until it is saturated. The results I have obtained in this way are not as good as when oxid of zinc alone has been used, but still they are sufficiently good for many purposes.

When I employ a zinc salt instead of oxid of zinc, I dissolve the zinc salt in the sulfite liquor, which is heated in an agitator-tank .zinc, whereby a chemical combination bewith a steam lead coil, as above mentioned, and I then add soda-ash or some other suitable base until a decided alkaline reaction is obtained by litmus-paper. The quantity of salt used varies greatly according to circumstancesas, for example, cheapness, the kind of liquor to be treated, and the purposes for which the product is intended; but I generally use a quantity representing from onetenth per cent. to two per cent. maid of zinc.

That I claim, and desire to secure by Letters Patent, is

1. The herein-described process or method of treating sulfite liquor which consists in submitting said liquor to the action of oXid of tween said oXid and some substances in said CARL DANIEL EKMAN.

Witnesses:

GEORGE O. BACON, ROBERT M. SPEARPOINT. 

